For example, a wireless power transfer system has been known as a system for charging a vehicle-driving battery of an electric vehicle, etc. In this system, a primary coil device (power transmission coil device) is installed on a ground side, a secondary coil device (power reception coil device) is installed on a vehicle side, and charging is performed by wirelessly transmitting power from the primary coil device to the secondary coil device using a principle of electromagnetic induction. For example, as described in Patent Literature 1, a primary coil device in which an electric wire is wound in a spiral shape on one side of a flat disc-shaped magnetic body core and a secondary coil device having the same configuration are disposed to face each other across a gap between coils thereof.
Various attachment structures for attaching such a coil device to a vehicle, etc. have been known. For example, in a structure described in Patent Literature 2, a mounting hole is provided in a cover made of a metal material, and a coil device is fixed to a vehicle using bolts, etc. In a structure described in Patent Literature 3, a coil device is fixed to a vehicle, or a coil device is fixed to a support member provided on a vehicle frame using bolts, etc.